Unsaturated polyester and epoxy-functional graded-rubber paint and process i

ABSTRACT

A RADIATION-CURABLE PAINT WHICH ON A PIGMENT AND PARTICULATE FILLER-FREE BASIS CONSISTS ESENTAILLY OF VINYL MONOMERS AND A UNIQUE, ALPHA-BETA OLEFINICALLY UNSATURATED, RUBBER-COMPRISING RESIN FORMED BY REACTING AN ALPH-BETA OLEFINICALLY UNSATURATED, MONOCARBOXY TERMINATED, POLYESTER HAVING AN ALPHA-BETA OLEFINICALLY UNSTATURATED DICARBOXYLIC ACID OR ANHYDRIDE AS A CONSTITUENT MONOMER THEROF WITH AN EPOXY-FUNTIONAL, GRADED-RUBBER PARICLE. THE DISPERSION IS APPLIED TO SUBSTRATES AS A PAINT FILM AND CURED THEREON BY EXPOSURE TO IONIZING RADIATION, E.G., AN ELECTRON BEAM.

United States Patent @ffice 3,060,371 Patented May 2, 1972 US. Cl. 1.17-93.31 Claims ABSTRACT OF THE DISCLOSURE A radiation-curable paintwhich on a pigment and particulate filler-free basis consistsessentially of vinyl monomers and a unique, alpha-beta olefinicallyunsaturated, rubber-comprising resin formed by reacting an alpha-betaolefinically unsaturated, monocarboxy terminated, polyester having analpha-beta olefinically unsaturated dicarboxylic acid or anhydride as aconstituent monomer thereof with an epoxy-functional, graded-rubberparticle. The dispersion is applied to substrates as a paint film andcured thereon by exposure to ionizing radiation, e.g., an electron beam.

THE INVENTION A unique, rubber-comprising, a radiation-curable paint isprovided by preparing a film-forming dispersion of vinyl monomers and analpha-beta olefinically unsaturated, rubber-comprising resin formed byreacting an alpha-beta olefinically unsaturated, monocarboxylic acidterminated polyester having an alpha-beta olefinically unsaturateddicarboxylic acid or anhydride as a constituent monomer thereof with anepoxy-functional, crosslinked, acrylic, graded-rubber particle. Thedispersion is applied to substrates, e.g., wood, glass, shaped polymericsolid, etc., as a paint film and cured thereon by ionizing radiation,preferably an electron beam having average energy in the range of about100,000 to about 500,000 electron volts.

(1) The polyester reactant The alpha-beta olefinically unsaturatedmonocarboxylic acid terminated polyester used in the preparation of theresinous component of the paints herein advantageously have averagemolecular weight in the range of about 1,000 to about 5,000, commonly inthe range of about 1,500 to about 3,500. The polyester advantageouslyhas about 0.5 to about 5, preferably about 0.7 to about 3.5 units ofalpha-beta olefinic unsaturation per 1,000 units molecular weight.

These polyesters consist essentially of carbon, hydrogen and oxygen andcan be prepared by conventional methods for producing polyesters andusing as constituent monomers a monocarboxylic acid, maleic anhydride(or dicarboxylic acid or anhydride of equivalent olefinic unsaturation),a second anhydride wherein the anhydride group is supported by a ringstructure, e.g., phthalic anhydride and a polyhydric alcohol, e.g.,propylene glycol.

The alpha-beta olefinic unsaturation of the polyester employed as areactant in preparing the rubber-comprising resins used herein isderived from an alpha-beta olefinically unsaturated dicarboxylic acidand/ or anhydride constituent monomer, e.g., maleic, fumaric, itaconic,chloromaleic, dichloromaleic, etc.

The anhydride wherein the anhydride group is attached to a ringstructure (aromatic or aliphatic) is selected from anhydrides that Willnot provide additional alphabeta olefinic unsaturation units and therelative quantities of the two acids and/ or anhydrides are adjusted toprovide the desired concentration of such unsaturation. Suitableanhydrides for this purpose include, but not by way of limitation,phthalic, tetrahydrophthalic, cyclohexane dicarboxylic acid anhydride,nadich methyl anhydride, etc.

The polyhydric alcohol is preferably a diol consisting essentially ofcarbon, hydrogen and oxygen. Triols and other multihydric alcohols canbe used but it is advisable to employ such alcohols in minor amountswith a diol, if they are used at all. Suitable diols include, but not byway of limitation, ethylene glycol, propylene glycol, 1,3- butyleneglycol, 2-butene-1,4 diol, 1,4-butane glycol, 1,6- hexamethylene glycol,dimethylol benzenes, dihydroxy ethyl benzenes, etc.

(H) Preparation of the graded-rubber particle The graded-rubber particlehas a core of crosslinked, elastomeric, acrylic polymer, an outer shellcomprising methyl methacrylate and an epoxy-functional acrylate and anintermediate layer which is a copolymer of the monomers used to form thecore and the monomers used to form the outer shell.

The process for preparing these particulate materials is at least atwo-stage process. In one method of preparation, a major amount ofmonofunctional monoacrylate is emulsion copolymerized in the first stagewith a crosslinking amount of a dior tri-functional monomer containingtwo or more non-conjugated terminal ethylenic groups, preferably adiacrylate, using a water-soluble free radical initiator and a suitablesurfactant to yield a latex of relatively uniform particle size, e.g.,0.04 to 1 micron average diameter. Before this reaction reachessubstantial completion, i.e., when the reaction is between about 50 andabout 90, preferably between about 70 and about 89, percent complete,the second monomeric component, i.e., a mixture of about 65 to about 98,preferably about 70 to about 95, mole percent methyl methacrylate, andabout 2 to about 35, preferably about 5 to about 30 mole percent of anepoxy-functional acrylate, e.g., glycidyl methacrylate, or a mixture ofabout 2 to about 35, preferably to about 30 mole percentepoxy-functional acrylate and about 65 to about 98 mole percent of amonomer mixture selected from and consisting essentially of esters ofacrylic or methacrylic acid and a C -C monohydric alcohol, monovinylhydrocarbons, diacrylates and divinyl hydrocarbons, is added slowly tothe reaction mixture. The polymerization process is continuedto yield astable latex of relatively uniform particle size and composition. Asurfactant is used in forming the emulsion and additional surfactant maybe added simultaneously with the second stage monomeric component.

The latex is coagulated, Washed and dried to yield a finely dividedwhite powder suitable for use in this invention. Generally, theparticles are prepared from monomers that will provide a crosslinkedacrylic, rubber-like core and a glass-like polymeric outer shell at roomtemperature, e.g., 20-30 C. The terms rubber-like and glass-like are, ofcourse, meaningless except when used in reference to a specifictemperature or temperature range. The particles should be formulated sothat the core retains its rubber-like properties and the outer shellretains its glass-like properties at temperatures encountered byarticles of commerce in the intended field of use. Hence, for practicalpurposes, the monomers should be selected so that the core has a glasstransition temperature that is substantially below that of the outershell. Advantageously, the difference in glass transition temperaturebetween the core and the shell is at least 50 C., preferably above 100C.

The core is formed from a major amount of an alkyl, monofunctional,monoacrylate and a crosslinking amount of a dior tri-functional monomercontaining 2 or more non-conjugated terminal ethylenic groups. Themonofunctional, alkyl, monoacrylate is preferably an ester of a C -Cmonohydric alcohol and acrylic acid, e.g., ethyl acrylate, butylacrylate, hexyl acrylate, Z-ethyl hexyl acrylate and/or mixtures of thesame. Certain other alkyl acrylates may be used when the crosslinkedpolymer thereof has an appropriate glass transition temperature, e.g.,dodecyl methacrylate. Butyl acrylate and '2-ethyl hexyl acrylate are themost preferred of the monoacrylates for use in forming the core. Thepolymers produced from most methacrylates have glass transitiontemperatures which are too high to provide rubberlike properties atnormally encountered temperatures. Hence, except for special useapplications, the monoacrylate component of the core will be either anester (or esters) of acrylic acid or a mixture of a major amount of thesame and a minor amount of methacrylate.

Suitable crosslinking agents include, but not by way of limitation,1,3-butylene diacrylate, 1,3-butylene dimethacrylate, divinyl benzene,1,6-hexamethylene diacrylate, 1,6-hexamethylene dimethacrylate,1,1,1-trimethylolethane triacrylate, 1,1,l-tetrimethylolethanetrimethacrylate, l,l,l-trimethylolpropane triacrylate,1,1,l-trimethylolpropane trimethacrylate, l,4,-dimethylolcyclohexanedimethacrylate, allyl acrylate, allyl methacrylate, methallyl acrylate,methallyl methacrylate, diallyl maleate, diallyl fumarate, and diallylphthalate. In one embodiment, the crosslinking agent is a diester ofacrylic or methacrylic acid and a C -C preferably C C dihydric alcohol.In another embodiment, the crosslinking agent is a triester of acrylicor methacrylic acid and a C C preferably C C trihydric alcohol.

In the first reaction stage, there is preferably employed about 80 toabout 98 mole percent of a monofunctional, monoacrylate and about 20 toabout 2 mole percent of the crosslinking agent.

In the second stage reaction, it is preferred to use a mixture of about65 to about 98, preferably about 70 to about 95 percent methylmethacrylate and about 2 to about 35, preferably about 5 to about 30,mole percent of epoxyfunctional acrylate. These are added before thefirst reaction ceases. The amounts of the second stage reactantsrelative to the combined first stage reactants may vary widely dependingupon the physical properties desired in the final product, i.e., fromabout to about 90 to about 90 to about 10 weight percent.

The methyl methacrylate concentration in the outer shell is advisedly atleast about 30 mole percent with the balance of the monofunctionalcomponent being made up of monofunctional monoacrylates, e.g., esters ofO C monohydric alcohols and either acrylic or methacrylic acid, ormonofunctional vinyl hydrocarbons such at styrene, methyl substitutedstyrenes, e.g., alpha methyl styrene, vinyl toluene etc. It will also beadvantageous at times to have a limited amount of crosslinking in theouter shell and hence to include in said balance a minor amount of adiacrylate, e.g., l to 30 mole percent of a. diester of acrylic ormethacrylic acid and a C -C preferably C -C dihydric alcohol, or divinylhydrocarbon, e.g., 1 to 30 mole percent of divinyl benzene. The physicalproperties of the outer shell may also be modified by replacing up toabout 30 mole percent of the methyl methacrylate with acrylonitrile ormethacrylonitrile.

The initial monomer charge is usually emulsified by one or moremicelle-forming compounds composed of a hydrophobic part, such as ahydrocarbon group containing 8 or more carbon atoms, and a hydrophilicpart, such as alkaline metal or ammonium carboxylate groups, phosphateor sulfate partial ester groups, sulfonate groups, and the like.Exemplary emulsifying agents include alkali metal sulfonates of styrene,naphthalene, decyl benzene and dodecyl benzene; sodium dodecyl sulfate;sodium stearate; sodium oleate; sodium alkyl aryl sulfonates;polyoxyethylene sulfates and phosphates; the ethylene oxide condensatewith long chain fatty acids, alcohols, and mercaptans and the alkalimetal salts of rosin acids.

These materials and techniques of employment of emulsion formation andmaintenance are well known to the art and have no unusual applicationhere. As they are conventional materials employed in a conventionalmanner further description is unnecessary.

The polymerization initiator is composed of one or more Water-soluble,free-radical-generating species such as hydrogen peroxide or sodium,potassium, or ammonium persulfates, perborates, peracetates,percarbonates and the like. As is well known in the art, theseinitiators may be associated with activating systems such as redoxsystems which may incorporate mild reducing agents such as sulfites andthiosulfites and redox reaction promotors such as transition metal ions.

A chain transfer agent or a mixture of chain transfer agents may beadded to the reaction medium to limit the molecular weight of thepolymer. Such chain transfer agents are generally mercaptans such asdodecane thiol, pentane thiol, and butane thiol.

Those skilled in the art will be aware that other emulsifying agents,polymerization initiators and chain transfer agents may be used whencompatible with the polymerization system herein employed.

The reaction may be carried out at temperatures from about 40 C. toabout C., or at lower temperatures, as from 0 C. to 80 C. in the case ofactivated systems.

The graded-rubber particles above-described and this method ofpreparation are disclosed by Ray A. Dickie and Seymour Newman in theirpatent application Ser. No. 100,464 filed of even date with thisapplication.

In another method of preparation, hereinafter illustrated, the rubberparticles are formed in an aliphatic hydrocarbon medium.

(III) Vinyl monomers employed in the paint dispersion The paint binderdispersion advantageously contains about 20 to about 80, preferablyabout 25 to about 75, weight percent vinyl monomers and about 20 toabout 80, preferably about 25 to about 75, weight percent of thepolymeric component, i.e., the alpha beta olefinically unsaturated,rubber-comprising resin formed by reacting the aforedescribed alpha-betaolefinically unsaturated, mono carboxy-functional polyester with theaforedescribed hydroxy-functional, acrylic, graded-rubber particle.Obviously, the polymeric component may also contain other alpha-betaolefinically unsaturated resins such as those disclosed in US. Pats.3,437,512; 3,437,513; 3,437,514 and 3,509,234.

Monomer type and concentration provide one means for adjusting theviscosity of the paint dispersion to conform to the methods ofapplication desired, e.g., spray coating, roll coating, etc. Infunctional terms, the amount of vinyl monomer present is at leastsufficient to convert the alpha-beta olefinically unsaturated,rubber-comprising resin into a crosslinked continuous coating on thesurface of a substrate when a film of such coating dispersion is exposedto ionizing radiation, e.g., electron beam.

Vinyl monomers employed may be monofunctional, monoacrylates formed bythe esterification of acrylic or methacrylic acid and a C -C preferablya C -C monohydric alcohol, e.g., methyl methacrylate, ethyl acrylate,butyl acrylate, butyl methacrylate, 2-ethyl hexyl acrylate, etc. Themonomer mixture may also include a minor amount, e.g., 1 to 0 molepercent of diacrylates, e.g., the diesters of acrylic or methacrylicacid and a C -C diol such as 1,3-butylene diacrylate, 1,3-butylenedimethylacrylate,1,6-hexamethylene diacrylate, 1,6-hexamethylenediacrylate, 1,6-hexamethylene dimethacrylate, ethylene glycoldimethacrylate, etc.

Monovinyl hydrocarbons, e.g., styrene, alpha methyl styrene, vinyltoluene, etc., may also be used either alone or in combination with theaforementioned monoacrylates. Minor amounts, e.g., about II to about 30mole percent of the vinyl monomer mixture may be made up of divinylhydrocarbons such as divinyl benzene. Other vinyl monomers, e.g.,acrylonitrile, methacrylonitrile, vinyl acetate, etc., may be employedin minor amounts, e.g., about 1 to about 30 mole percent.

Advantageously, at least 70 weight percent of the vinyl monomercomponent is made up of monoacrylates selected from esters of a C Cmonohydric alcohol and acrylic or methacrylic acid and/ or monovinylhydrocarbons having about 8 to about 9 carbon atoms. Frequently, it isadvantageous to use a mixture of about 40 to about 60 mole percent ofthese monoacrylates and about 60 to about 40 mole percent of thesemonovinyl hydrocarbons.

(IV) Preparation and application of the coating dispersion to asubstrate By adjusting the viscosity of the coating dispersion to aviscosity compatible with the desired method of coating, these coatingsmay be applied by any of the conventional methods, e.g., brushing,spraying, roll coating, curtain coating, flow coating, etc.

The viscosity of the paint binder solution may be adjusted by varyingthe molecular weight of the alpha-beta olefinically unsaturated,rubber-comprising resin. This may be accomplished by controlling theaverage number of functional groups per graded-rubber particle bycontrolling the concentration of hydroxyl bearing monomer in the outershell, particularly in the final portion of the monomer mixtureintroduced into the reaction medium when the graded-rubber particle isproduced. The viscosity may also be regulated by varying the relativeconcentration of the resin component with respect to the vinyl monomercomponent and/ or by varying the relative concentrations of dissimilarmonomers within the vinyl monomer component. The binder dispersion maybe applied to the substrate essentially free of non-polymerizable,organic solvents and/or diluents or it may be applied with the solventand/or diluents in a method of application wherein the solvents and/ordiluents are flashed otf prior to polymerization.

Coatings may be applied to any substrate, e.g., metal, wood, glass,polymeric solids, etc. These coatings will ordinarily be applied to anaverage depth in the range of about 0.1 to about 4 mils, more commonlyabout 0.5 to about 2 mils.

(V) Curing the coatings Films formed of the paints of this invention canbe cured with ionizing radiation at relatively low temperatures, e.g.,room temperature (20 to 25 C.) or a temperature between room temperatureand that temperature at which significant vaporization of its mostvolatile component is initiated, ordinarily between 20 C. and 75 C. Theradiation energy is applied at dose rates of about 0.1 to about 100 Mradper second on a workpiece, preferably a moving workpiece, with thecoating receiving a total dose in the range of about 1 to about 25,commonly about 8 to about 15 Mrad.

The term ionizing radiation as employed herein means radiation havingsufficient energy to remove an electron from a gas atom, forming an ion,hence radiation with minimum energy of, or equivalent to, at least about5,000 electron volts except when the curing is carried out in a vacuum.The preferred method of curing films of the instant paint binders on thesubstrates to which they have been applied is by subjecting such filmsto a beam of polymerization eifecting electrons which at its source ofemission is within the range of, or equivalent to, about 100,000 toabout 500,000 electron volts. If irradiation is carried out in vacuum orat reduced pressure, this energy range may be considerably lower. Inthis method of curing, it is preferred to employ a minimum of about25,000 volts per inch of distance between the radiation emitter and theworkpiece where the intervening space is occupied by air or other gas ofcomparable density. Adjustment is made for the relative resistance ofthe intervening gas which is preferably an oxygen-free, inert gas suchas nitrogen or helium.

In this application, the term paint is meant to include finely groundpigment and/or filler in the binder, the binder without pigment and/orfiller or having very little of the same, which can be tinted, ifdesired. Thus, the binder, which is ultimately converted to a durablefilm resistant to wear, weather, etc. can be all or virtually all thatis used to form the film or it can be a vehicle for pigmentary and/ ormineral filler material.

The abbreviation Mrad as employed herein means one million rad. The termrad as employed herein means that dose of radiation which results in theabsorption of ergs of energy per gram of absorber, i.e., coating film.The electron emitting means may be a linear electron accelerator capableof producing a direct current potential in the range hereinbeforementioned. In such device, electrons are ordinarily emitted from a hotfilament and accelerated through a uniform voltage gradient. Theelectron beam, which may be about /8 inch in diameter at this point, isthen scanned in one direction to make a fanshaped beam and then passedthrough a metal window, e.g., aluminum, aluminum-copper alloy, ormagnesiumthorium alloy of about 0.003 inch thickness. This inventionwill be more fully understood from the following examples:

EXAMPLE 1 (A) Preparation of the graded-rubber particles Graded-rubberparticles are prepared in aqueous medium using the following procedures:To 1,000 parts by weight water which has been boiled and cooled to roomtemperature under a nitrogen atmosphere are added 2.86 parts by weightsodium dodecyl sulfate dissolved in 35.7 parts by weight water and about/6 of a monomer mixture consisting of 348 parts by weight butyl acrylateand 32.3 parts by weight 1,3-butylene dimethacrylate. The mixture isstirred to establish dispersion of the monomers. To the stirred mixtureare added 3.14 parts by weight potassium persulfate dissolved in 71.4parts by weight water and the mixture is heated to 45 C. After about 10minutes addition of the remainder of the first monomer mixture is begunat a rate such that the tem perature of the reaction mixture ismaintained at 47 to 49 C. The last half of the first monomer mixture isadded simultaneously with 2.86 parts by weight of sodium dodecyl sulfatedissolved in 35.7 parts by weight water. Addition of the first monomermixture requires about 45 minutes. The reaction mixture is maintained at47 to 49 C. for 35 minutes prior to beginning simultaneous dropwiseaddition of a mixture of 236 parts by weight methyl methacrylate, 143.4parts by weight glycidyl methacrylate, and 2.57 parts by weightl-dodecane thiol and a solution of 5.72 parts by weight sodium dodecylsulfate in 35 .7 parts by weight water. This addition, which requiresabout 40 minutes, is carried out at such a rate that the temperature ofthe reaction mixture is maintained at 48 to 49 C. Following thisaddition, the reaction mixture is maintained within the last-mentionedtemperature range for an additional two hours. The resulting latex iscooled to room temperature and neutralized with aqueous ammonia. Theoverall conversion of monomers is about 9 8%. The size of theseparticles is found to be in the range of 0.1 to 0.2 micron.

(B) Determination of epoxy concentration Determination of theconcentration of the reactive epoxy groups in the shell of thegraded-rubber particles is made by the method involving addition oftetraethylammonium bromide followed by titration with perchloric acid inacetic acid using crystal violet as indicator. This method is describedby R. R. Jay in Analytical Chemistry, vol. 36, page 667 (1964).

(C) Preparation of monocarboxy terminated Unsaturated polyester Asalpha-beta olefinically unsaturated monocarboxy terminated polyester isprepared by the following method using the materials hereinafter setforth:

Materials: Parts by weight Phthalic anhydride 296 Maleic anhydride 98Propylene glycol 228 Stearic acid 85 Dibutyl tin oxide 3 Procedure Theabove-listed reactive monomers and the catalyst dibutyl tin oxide arecharged to a 3-necked flask fitted with stirrer, condenser and nitrogeninlet. The mixture is heated at 180 C. for 2 hours. The temperature isthen raised to 200 C. and glycol and water slowly distilled off untilthe carboxyl number of the polyester is in the range of about 22 toabout 37 and the ratio of carboxyl to hydroxyl is about 25. Theunsaturated polyester thus obtained contains an average of about 1 freecarboxyl group per molecule and has molecular weight in the range ofabout 1500-2000. Under these conditions with these materials a minoramount of polyester will be produced having two carboxyl groups permolecule as well as a minor amount of polyester having no free carboxylgroups per molecule. The production of these materials is minimized byproper proportioning of constituent monomers and intimate mixing ofreactants during polyester formation. A reaction product containing lessthan about 30 mole precent of the dicarboxylic polyester and less thanabout mole percent of the polyester without carboxyl is suitable for usein this invention. Preferably, the monocarboxy terminated polyestercomprises in excess of 88 mole percent of the reaction product.

The carboxyl number and the hydroxyl number are determined by titrationand the molecular weight is calculated therefrom using the methodsdescribed in Preparative Method of Polymer Chemistry by W. R. Sorensonand T. W. Campbell, Interscience Publishers, New York, New York, USA.(1961) at page 134.

(D) Reaction of polyester with graded-rubber particles To one (1) partby weight of the monocarboxylie terminated polyester of C is added ten(10) parts by weight of methyl methacrylate, epoxy-functionalgraded-rubber particles from I in an amount providing one epoxy groupper each carboxy group on the polyester component, 0.1 part by weighttetrabutyl ammonium chloride. These materials are charged to a flaskequipped with stirrer, condenser and nitrogen inlet. The contents areheated at 75 C. for 1 6 hours.

The amount of methyl methacrylate monomer (or other acrylic monomers) isnot critical. Acrylic monomers act as solvent medium for this reaction.They are preferably used in an amount such that after reaction of thepolyester and graded-rubber the reaction mixture will possess thedesired viscosity for painting. If the concentration of monomers afterreaction is excessive, it may be removed by distillation under reducedpressure. If the concentration of monomers is deemed inadequate at thisstage, the desired viscosity can be achieved by adding monomers.

In this instance, the methyl methacrylate concentration is adjusted toprovide a paint binder dispersion containing 50 weight percent methylmethacryalte and 50 weight percent of the polymeric reaction product ofthe polyester and the graded-rubber particles.

(E) Coating of the substrate This dispersion, which is now ready forpigmentation if desired, is applied to the substrate surfaces, i.e.,wood, metal, glass, and shaped polymeric solid(acrylonitrilebutadiene-styrene copolymer), to the average depth ofabout 0.7 mil (0.0007 inch) and cured by exposure to electron beamradiation. The conditions of irradiation are as follows:

Potential: 275 kv.

Current: 30 ma.

Distance, emitter to workpiece: 10 in. Dose: 10-15 Mrad Atmosphere:nitrogen EXAMPLE 2 (A) Preparation of the graded-rubber particlesGraded-rubber particles having epoxy functionality are prepared as inExample 1 with changes in the composition of the core and of the outershell. In the core, an equimolar amount of 1,3-butylene diacrylate issubstituted for the 1,3-butylene dimethacrylate and an equimolar amountof 2-ethyl hexyl acrylate is substituted for the butyl acrylate. Theouter shell is formed from a mixture of monomers consisting of 40 molepercent methyl methacrylate, 20 mole percent glycidyl methacrylate, 5mole percent ethyl acrylate, 5 mole percent butyl acrylate, 5 molepercent butyl methacrylate, 5 mole percent 2-etyhl hexyl acrylate, 5mole percent styrene, 5 mole percent vinyl toluene, 5 mole percent1,3-butylene diacrylate, and 5 mole percent divinyl benzene. Thismonomer mixture excluding the glycidyl methacrylate and the methylmethacrylate is divided into three equal portions. The first twoportions are added slowly to the reaction mixture. The third portion ismixed with the glycidyl methacrylate and methyl methacrylate and addedlast.

(B) Determination of epoxide concentration Determination of theconcentration of the reactive epoxy groups on the surfaces of theparticles is carried out using the method described in Example 1.

(C) Preparation of polyester An alpha-beta olefinically unsaturated,monocarboxy terminated polyester is prepared by the following methodusing the materials hereinafter set forth:

Materials: Parts by weight Phthalic anhydride 296 Maleic anhydride 98Propylene glycol 228 Procedure The above-listed monomers with 3 parts byWeight dibutyl tin oxide are charged to a 3-necked flask fitted withstirrer, condenser and nitrogen inlet. The mixture is heated to C. for 2hours. The temperature is then raised to 200 C. and Water and propyleneglycol are distilled off slowly. During this process, samples ofpolyester are taken and analyzed for their carboxyl and hydroxyl numbersusing the same method used in Example 1. The distillation is stoppedwhen the ratio of carboxyl number to hydroxyl number is about 30 and thecarboxyl number is between about 22 and 37. The number average molecularweight of the polyester is calculated from hydroxyl and carboxyl number(method described in aforecited publication of Sorenson and Campbell atpage 134) is in the range of about 1500 to about 2500.

The polyester at this stage is a linear polymer terminated with carboxylgroups, i.e., it has an average of nearly two carboxyl groups perpolyester molecule.

To the reaction mixture is added 45 parts by weight of diethylene glycolmonoethyl ether, also called 2-2-ethoxyethoxy-ethanol. Heat is continuedat 200 C. until the carboxyl number of the polyester is reduced by about50%. The polyester is then ready for reaction with the graded-rubberparticles.

(D) Reaction of the polyester with the graded-rubber The procedure usedfor this reaction step in Example 1 is repeated.

(E) Coating of the substrate The procedure used for application andcuring in Example 1 is repeated.

EXAMPLE 3 The procedures of Examples 1 and 2 are repeated with thedifference that a vinyl monomer mixture consisting of 2 molar partsmethyl methacrylate, 1 molar part ethyl acrylate and 1 molar part2-ethyl hexyl acrylate is substituted for the methyl methacrylatecomponent of the paint.

EXAMPLE 4 The procedures of Examples 1 and 2 are repeated with thedifference that a vinyl monomer mixture consisting of 2 molar partsmethyl methacrylate, 1 molar part methyl styrene and 1 molar part butylacrylate is substituted for the methyl methacrylate component of thepaint.

EXAMPLE 5 The procedures of Examples 1 and 2 are repeated with thedifference that a vinyl monomer mixture consisting of 2 molar partsstyrene, 1 molar part 1,3-butylene dimethacrylate, and 1 molar partmethyl methacrylate is substituted for the methyl methacrylate componentof the paint.

EXAMPLE 6 The procedures of Examples 1 and 2 are repeated with thedifference that a vinyl monomer mixture consisting of 2 molar partsmethyl methacrylate, 1 molar part styrene, and 1 molar part divinylbenzene is substituted for the methyl methacrylate component of thepaint.

EXAMPLE 7 The procedures of Examples 1 and 2 are repeated with thedifference that 304 parts by weight tetrahydrophthalic anhydride issubstituted for the phthalic anhydride used in preparing the polyester.

EXAMPLE 8 The procedures of Examples 1 and 2 are repeated with thedifference that 296 parts by weight isophthalic anhydride is substitutedfor the phthalic anhydride used in preparing the polyester.

EXAMPLE 9 The procedures of Examples 1 and 2 are repeated with thedifference that 308 parts by weight cyclohexane dicarboxylic anhydridein substituted for the phthalic anhydride used in preparing thepolyester.

EXAMPLE 10 The procedures of Examples 1 and 2 are repeated with thedifference that 537 parts by Weight of dodecyl succinic anhydride issubstituted for the phthalic anhydride used in preparing the polyester.

EXAMPLE 11 The procedures of Examples 1 and 2 are repeated with thedieffrence that 356 parts by weight nadic methyl anhydride issubstituted for the phthalic anhydride used in preparing the polyester.

EXAMPLE 12 The procedures of Examples 1 and 2 are repeated with thedifference that 312 parts by weight of neopentyl glycol are substitutedfor the propylene glycol used in preparing the polyester.

EXAMPLE 13 The procedures of Examples 1 and 2 are repeated with thedifference that 186 parts by weight ethylene glycol are substituted forthe propylene glycol used in preparing the polyester.

EXAMPLE 14 The procedures of Examples 1 and 2 are repeated with Theprocedures of Examples 1 and 2 are repeated with the difference that 270parts by weight of 1,4-butylene diol are substituted for the propyleneglycol used in preparing the polyester.

EXAMPLE 16 The procedures of Examples 1 and 2 are repeated with thedifference that 112 parts by Weight itaconic anhydride is substitutedfor the maleic anhydride used in preparing the polyester.

EXAMPLE 17 The procedures of Examples 1 and 2 are repeated with thedifference that 67 parts of weight lauric acid is substituted for thestearic acid used in preparing the polyester.

EXAMPLE 18 The procedures of Examples 1 and 2 are repeated with thedifference that 39 parts by weight of caproic acid are substituted forthe stearic acid used in preparing the polyester.

EXAMPLE 19 The procedures of Examples 1 and 2 are repeated with thedifference that 39 parts by weight isocaproic acid are substituted forthe stearic acid used in preparing the polyester.

EXAMPLE 20 The procedures of Examples 1 and 2 are repeated with thedifference that 48 parts by weight caprylic acid are substituted for thestearic acid used in preparing the polyester.

EXAMPLE 21 The procedures of Examples 1 and 2 are repeated with thedifference that an equimolar amount of fumaric acid is substituted forthe maleic anhydride in the preparation of the polyester.

EXAMPLE 22 The procedures of Examples 1 and 2 are repeated except forthe preparation of the epoxy-functional gradedrubber particles. Thecores of the particles are here formed from about mole percent butylacrylate and about 15 mole percent divinyl benzene, and the outer shellsare here formed from a monomer mixture consisting of 30 mole percentmethyl methacrylate, 15 mole percent alpha methyl styrene, 10 molepercent ethyl acrylate, 10 mole percent acrylonitrile, 10 mole percentmethacrylonitrile, 10 mole percent butyl methacrylate, 5 mole percentvinyl acetate and 10 mole percent glycidyl acrylate. The monomers usedto form the outer shell excepting the glycidyl acrylate are divided intothree portions. After the first two portions are slowly added to thereaction mixture, the final portion is mixed with the glycidyl acrylateand added dropwise to the reaction mixture.

EXAMPLE 23 The procedures of Examples 1 and 2 are repeated except forthe preparation of the epoxy-functional graded-rubber particles. Thecores of the particles are here formed from about mole percent ethylacrylate and about 10 mole percent of 1,1,l-trimethylolpropanetrimethacrylate.

EXAMPLE 24 The procedures of Examples 1 and 2 are repeated except forthe preparation of the epoxy-functional graded-rubber particles. Thecores of the particles are here formed from about 90 mole percent2-ethyl hexyl acrylate and about 10 mole percent of1,4-dirnethylolcyclohexane dimethacrylate.

1 1 EXAMPLE 2s The procedures of Examples 1 and 2 are repeated exceptfor the preparation of the epoxy-functional graded-rubber particles. Thecores of the particles are here formed from about 90 mole percent butylacrylate and about mole percent divinyl benzene.

EXAMPLE 26 The procedures of Examples 1 and 2 are repeated except forthe difference that the curing of the coatings upon the substrates iscarried out using an electron beam having an average potential of about260,000 electron volts.

EXAMPLE 27 The procedures of Examples 1 and 2 are repeated except forthe differences that the curing of the coatings upon the substrate iscarried out using the helium atmosphere and an electron beam having anaverage potential of about 150,000 electron volts.

EXAMPLE 28 The procedures of Examples 1 and 2 are repeated except forthe differences that the curing of the coating upon the substrates iscarried out using an atmosphere comprising a major amount of nitrogenand a minor amount of carbon dioxide and an electron beam having anaverage potential of about 325,000 electron volts.

EXAMPLE 29 The procedures of Examples 1 and 2 are repeated with thedifferences that the coating dispersion consists essentially of 80 partsby weight of the alpha-beta olefinically unsaturated polyester andgraded-rubber reaction product and about 20 parts by weight of vinylmonomers. The vinyl monomers are a mixture of equimolar amounts ofmethyl methacrylate and styrene.

EXAMPLE 30 EXAMPLE 31 The procedures of Examples 1 and 2 are repeatedwith the difference that the coating consists essentially of 50 parts byweight of the alpha-beta olefinically unsaturated polyester andgraded-rubber reaction product and about 50 parts by weight of vinylmonomers. The vinyl monomers are a mixture of 50 mole percent styrene,30 mole percent methyl methacrylate, 20 mole percent butyl methacrylateand 10 mole percent 1,4-dimethylolcyclohexane dimethacrylate.

EXAMPLE 32 The procedure of Examples 1 and 2 are repeated with thedifference that the coating dispersion consists essentially of 20 partsby weight of the alpha-beta olefinically unsaturated polyester andgraded-rubber reaction product and about 80 parts by weight of vinylmonomers. The vinyl monomers are a mixture of 85 mole percent methylmethacrylate and mole percent divinyl benzene.

EXAMPLE 33 The procedure of Examples 1 and 2 are repeated with thediiference that the epoxy-functional graded-rubber particles areprepared in the following manner:

(A) A mixture is formed from the following:

12 Materials: Grams Ethyl acrylate 80.0 1,3-butylene dimethacrylate 20.0Dispersing agent 3.0 AIBN 1.0

1 An amphiphtie copolymer (1 portion soluble in the acrylic monomers andthe other portion soluble in the solvent, e.g., dodecane) is prepared byreacting 12l1ydroxystearic acid (300 g.) in the presence of stearylalcohol (310 g.) and p-toluene sulfonic acid (6 g.) at 180-190 C. untilthe acid value is less than 1 mg. KOH/g. The product is then reactedwith methacrylic anhydride (170 g.). The resulting material is thencopolymerized with an equal amount of methyl methacrylate using AIBNinitiator (9 g.) and butyl acetate solvent. This method of producingthis dispersing agent is described in detail by K. E. J. Barratt and H.R. Thomas, Journal of Polymer Science, Part A1 vol. 7, 2625 (1969).Other dispersing agents which are effective for stabilizing suspensionin hydrocarbon liquids may be used in place of the above describedmaterial.

2 2,2 azobis-(2-methyl propionitrile).

(B) The mixture of the above listed material is added to 1,000 gramsn-dodecane under nitrogen. The mix is warmed to 40 C. When the exothernstarts the temperature is allowed to rise to C. The temperature ismaintained at 80 C. for 30 minutes.

(C) The reaction mixture is maintained in a nitrogen atmosphere andthere is added slowly with stirring a mixture of the followingmaterials:

Materials: Grams Methyl methacrylate 320.0 Glycidyl methacrylate 88.0Dispersing agent 3.0 AIBN 6.0

n-dodecane 1000.0

1 Same as in A.

EXAMPLE 34 The procedures of Examples 1 and 2 are repeated except forthe difference that the polyester and gradedrubber reaction product isformed from 0.25 molar part of the alpha-beta olefinically unsaturatedmonocarboxy terminated polyester and 1 molar part of theepoxy-functional graded-rubber particles.

'EXAMPLE 35 The procedures of Examples 1 and 2 are repeated except forthe difference that the polyester and gradedrubber reaction product isformed from 0.5 molar part of the monocarboxy terminated polyester and 1molar part of the epoxy-functional graded-rubber particles.

The terms acrylate and acrylates, when used herein without a modifierdistinguishing between esters of acrylic acid and methacrylic acid,shall be understood to include both. This, of course, does not apply toa naming of a specific compound.

It will be understood by those skilled in the art that modification canbe made within the foregoing examples in the scope of this invention ashereinbefore described and hereinafter claimed.

What is claimed is:

1. A radiation-curable paint which on a pigment and mineral filler-freebasis comprises a film-forming dispersion of about 80 to about 20 weightpercent vinyl monomers and about 20 to about 80 weight percent of apolymeric component consisting essentially of the product formed byreacting about 0.25 to about 1 molar part of an alpha-beta olefinicallyunsaturated, monocarboxy terminated polyester having an alpha-betaolefinically unsaturated dicarboxylic acid or anhydride and a polyhydricalcohol as constituent monomers thereof with one molar part of anepoxy-functional particles of graded-rubber, said molar part ofepoxy-functional particles of graded rubber being measured by andequivalent to one molar part of reactive epoxy groups on the surfacesthereof, said polyester having a molecular weight range of about 1,000to about 5,000 and from 0.5 to about 5 units of alpha-beta olefinicunsaturation per 1,000 units molecular 14 weight, and said particles ofgraded-rubber consisting esweight, and said particle of graded-rubberconsistsentially of ing essentially of (1) about 10 to about 90 weightpercent of a core of (1) about 10 to about 90 weight percent of acrosslinked acrylic polymer consisting essentially of core ofcrosslinked acrylic polymer consisting (a) about 80 to 90 mole percentof a monoester of 5 essentially of acrylic acid and a C -C monohydricalcohol, (a) about 80 to about 90 mole percent of a and monoester ofacrylic acid and a C -C (b) about 20 to about 2 mole percent of divinylm n hydric a cohol, and

benzene, a diester of acrylic or methacrylic acid about 20 to about 2mole Porcont of and a C -C dihydric alcohol, or a triester of 10 divinylbenz a diester of yl 0r acrylic or methacrylic acid and a C -Ctrimethacrylic acid and a 2- 8 dihydric hydric al h l, d cohol, or atriester of acrylic or methacryllc (2) about 90 to 10 weight percent ofan outer shell conacid and a ra y t' alcohol, and

sisting essentially of the polymerization product of about 90 to a o 10wolght Percent of an monomer mixtures selected from the group consistingOuter shell cohslstlbg ossontlallybt the P y f erization product ofmonomer mlxtures selected (a) about 65 to about 98 mole percent methylfrom the group conslstmg of methacrylate and about 2 to about 35 moleper- (a) about 65 to about 98 mole Percent math cent f an f ti lacrylate, and yl methacrylate and about 2 to about 35 (b) about 2 toabout 35 mole percent of an epoxymole Pfircent of an epoxy'funcuonalacry' functional acrylate and about 65 to about 98 late and mole percentof a mixture consisting essentially (b) about 2 to .about 35 molePercent of of esters of acrylic or methacrylic acid and a anepoxy'functlonal acrylate about 65 C -C monohydric alcohol, C -Cmonovinyl 9 t 98 3 percent of mlxture. conhydrocarbons, 0 to 30 molepercent of a difuncslstmg essenuauy of esters of acryhc or methacrylicacid and a C -C monohydric alcohol, C -C monovinyl hydrocarbons, 0 tomole percent of a difunctional compound selected from divinyl benzeneand diesters of acrylic or methacrylic acid and a C -C dihydric alcoholand 0 to 30 mole percent of a monomer selected from acrylonitrile,methacrylonitrile and vinyl acetate, and (B) crosslinking said film uponsaid substrate by exposing said film to a beam of electrons havingaverage energy in the range of about 100,000 to about tional compoundselected from divinyl benzene and diesters of acrylic or methacrylicacid and C -C dihydric alcohol and 0 to 30 mole percent of a monomerselected from acrylonitrile, methacrylonitrile and vinyl acetate. 30 2.A paint in accordance with claim 1 wherein said core is crosslinkedacrylic polymer consisting essentially of butyl acrylate and adiacrylate selected from 1,3-butylene diacrylate and 1,3-butylenedimethacrylate.

3; A paint in accordance with claim 1 wherein said core is crosslinkedacrylic polymer consisting essentially of y hexyl acrylate and adiacrylate Selected from 500,000 electron volts at its source ofemission. y e diacrylate and 1,3-b11tylene dimethacrylate- 9. The methodof claim 8 wherein said core is cross- A Palnt in accordance With Claim1 wherein Said linked acrylic polymer consisting essentially of butylacrygraded-rubber particles have average diameter in the range late anda diacrylate selected from 1,3-butylene diacrylate of about -f to about1 and 1,3-buty1ene dimethacrylate.

5. A palnt 1n accordance with claim 1 wherein said 10. The method ofclaim 8 wherein said core is crossvinyl monomers contain between 1 and30 mole percent linked acrylic polymer consisting essentially of Z-ethyl0f dlacrylateshexyl acrylate and a diacrylate selected from 1,3-butylene6. A paint in accordance with claim 1 wherein said diacrylate and1,3-butylene dimethacrylate. vinyl monomers are selected from esters ofacrylic acid 11'. The method of claim 8 wherein said graded-rubber and aC -C monohydric alcohol, esters of methacrylic Particles have averagediameter in the range of about acid and a C -C monohydric alcohol, C -Cmonovinyl to about 012 micronhydrocarbons, divinyl benzene, diesters ofacrylic acid and Tho method of Claim 8 wherein Said vhlyl a C -Cdihydric alcohol, and diesters of methacrylic omers contain between 1and 30 mole percent of diacryacid and a C -C dihydric alcohol. lates- 7.A paint in accordance with claim 1 wherein said The method of claim 3wherein Said Vinyl outer shell has glass transition temperature at least50 C. omers are Selected from esters of acrylic acid and a above that fid core, C monohydric alcohol, esters of methacrylic acid and a 8. Themethod of coating a substrate which comprises: CFC! {nfmohydric h C8-C9mobovinyl hydrocar (A) applying a u f f Said substrate a film of bons,divinyl benzene, diesters of acrylic acid anda C radiati nm paint whichon a pigment and C3 dihydric alcohol, and diesters of methacrylic acidand mineral filler-free basis comprises a film-forming disa caca dlhydncalcohol" persion of about 20 to about 80 weight percent of The th of dam8 wherem 5 outer shell i l monomers and about 80 to about 20 Weight hasglass transition temperature at least 50 C. above that percent of apolymeric component formed by reactof sald corei about 025 to about 1molar part of an a1pha beta 15. An article of manufacture comprising 1r1 combinabeta olefin'ically unsaturated, monoca-rboxy ter-rni- Substrateand Coatmg theme? the Hated polye'ster having an alphaibeta olefinioanylymerlzation product of a film-forming dlsperslon crosslinked in situ byionizing radiation, said film-forming dispersion on a pigment andparticulate filler-free basis consisting essentially of about 80 toabout 20 weight percent one molar part i an epoxy'functlonal Pamela ofof a polymeric component consisting essentially of the grade,d'mbber,sald one molar Part 9 an epoxy product formed by reacting about 0.25 to1 molar part of functlonal Pamela of graded'mbber bemg measured analpha-beta olefinically unsaturated, dicarboxylic acid saturateddicarboxylic acid or anhydride and a polyhydric alcohol as constituentmonomers thereof with by and equivalent to one molar P of reactile oranhydride andapolyhydric alcohol as constituent mon- P Y groups on theSurfaces thereof, Said Polyester omers thereof with one molar part of anepoxy-functional having a molecular Weight Tango of about 1,000 toparticle of graded-rubber, said molar part of epoxy-funcabout 5,000 andfrom 0.5 to about 5 units of alphational particle of graded-rubber beingmeasured by and beta olefinic unsaturation per 1,000 units molecularequivalent to one molar part of reactive epoxy groups on 15 the surfacesthereof, said polyester having a molecular weight range of about 1,000to about 5,000 and from 0.5 to about units of alpha-beta olefinicunsaturation per 1,000 units molecular weight, and said particles ofgradedrubber consisting essentially of (1) about to about 90 weightpercent of a core of crosslinked acrylic polymer consisting essentiallyof (a) about 80 to about 90 mole percent of a monoester of acrylic acidand a C C monohydric alcohol, and (b) about to about 2 mole percent ofdivinyl benzene, a diester of acrylic or methacrylic acid and a C Cdihydric alcohol, or a triester of acrylic or methacrylic acid and a C Ctrihydric alcohol, and (2) about 90 to about 10 weight percent of anouter shell consisting essentially of the polymerization product ofmonomer mixtures selected from the group consisting of (a) about 65 toabout 98 mole percent methyl methacrylate and about 2 to about molepercent of an epoxy-functional acrylate, and (b) about 2 to about 35mole percent of an epoxyfunctional acrylate and about to about 98 molepercent of a mixture consisting essentially of esters of acrylic 0rmethacrylic acid and a C -C monohydric alcohol, C -C monovinylhydrocarbons, 0 to 30 mole percent of a difunctional compound selectedfrom divinyl benzene and diesters of acrylic or methacrylic acid and C-C dihydric alcohol and 0 to 30 mole percent of a monomer selected fromacrylonitrile, methacrylonitrile and vinyl acetate.

10 References Cited UNITED STATES PATENTS 3,423,481 1/1969 Mizutani260-836 3,450,796 6/1969 Grilfin 260-885 15 3,502,745 3/1970 Minton260881 FOREIGN PATENTS 1,132,645 11/1968 Great Britain 260-836 20 PAULLIEBERMAN, Primary Examiner US. Cl. X.R.

